Tuyere for a blast furnace and a method for operating the tuyere to atomize combustible material fed into the tuyere by a shock wave

ABSTRACT

A method and an arrangement for operating a supersonic tuyere having a convergent and a divergent passage portion separated by a neck in such a manner so as to produce in the divergent passage portion a shock wave to atomize a combustible material fed in the region of the neck into the tuyere. The shock wave is produced by more or less restricting the open cross section of the neck, preferably by adjusting the axial position of a solid body in the convergent portion of the tuyere with respect to the neck, to maintain the pressure of a combustion sustaining material fed into the tuyere upstream of the convergene portion, during variation of the fed amount of such material within predetermined limits, at such a magnitude to assure production of a shock wave at the divergent portion.

Borgnat et a1.

[ NOV. 13, 1973 TUYERE FOR A BLAST FURNACE AND A METHOD FOR OPERATING THE TUYERE TO ATOMIZE COMBUSTIBLE MATERIAL FED INTO THE TUYERE BY A SHOCK WAVE Inventors: Daniel Borgnat, Senecourt; Henri Della Casa; Noel Jusseau, both of Metz, all of France Assignee: Institut De Recherches De La Siderurgie Francaise, Saint Germain-en-Laye, France Filed: Jan. 19, 1972 Appl. No.: 218,962

Foreign Application Priority Data Jan. 20, 1971 France 7101742 U.S. Cl 110/1825, 122/6.6, 266/41,

431/D1G. 8 Int. Cl 5/00 Field of Search 110/1825; 266/41;

122/6.6; 43l/DIG. 8

Demalander 110/1825 3,076,642 2/1963 Dhenein 266/41 3,596,894 8/1971 Duthion 266/41 FOREIGN PATENTS OR APPLICATIONS 115,641 7/1940 Australia 266/41 1,171,136 4/1957 France 110/1825 Primary Examiner-Kenneth W. Sprague Assistant Examiner-James C. Yeung Attorney-Michael S. Striker [57] ABSTRACT A method and an arrangement for operating a supersonic tuyere having a convergent and a divergent passage portion separated by a-neck in such a manner so as to produce in the divergent passage portion a shock wave to atomize a combustible material fed in the region of the neck into the tuyere. The shock wave is produced by more or less restricting the open cross section of the neck, preferably by adjusting the axial position of a solid body in the convergent portion of the tuyere with respect to the neck, to maintain the pressure of a combustion sustaining material fed into the tuyere upstream of the convergene portion, during variation of the fed amount of such material within predetermined limits, at such a magnitude to assure production of a shock wave at the divergent portion.

5 Claims, 5 Drawing Figures PATEN raw 1 3 :975

SHEET 10F l PATENTEU um 13 1975 SHEET 2 BF 4 WQQ PATENTEUNDY 13 I973 SHEET 38? 4 TUYERE FOR ABLAST FURNACE AND A METHOD FOR OPERATING THE TUYERE TO ATOMIZE COMBUSTIBLE MATERIAL FED INTO THE TUYERE BY A SHOCK WAVE BACKGROUND OF THE INVENTION The present invention relates to a supersonic tuyere and a method of operating the same to assure that flowable, preferably liquid combustible material fed into the tuyere is properly atomized before entering into a blast furnace.

It is well known that the possibility to inject a combustible liquid material into a blast furnace is closely related to the problem of properly atomizing and mixing the combustible material with the combustion sustaining material fed into the tuyere. In order to assure a proper atomization and mixing of the combustible material and to thus permit to increase the amount of the combustible material injected through the tuyere into a blast furnace, the present invention provides for a supersonic tuyere for blast furnaces in which the atomization of the combustible material is obtained by means of a shock wave produced in the divergent portion of the tuyere. Tests have shown that in this manner a perfect atomization of the combustible material can be obtained, which permits to considerably increase the amount of combustible material which can be injected into the blast furnace without producing carbon black, which, as known, is a major obstacle encountered in tuyeres known in the art to increase the amount of combustible material which can be injected into the blast furnace. Nevertheless it is evident that such tuyeres will not give satisfactory results if the shock wave is not formed in the divergent portion of the tuyere. On the other hand, it is well known to calculate the convergent-divergent passage portion through the tuyere in such a manner to pass the blast at supersonic speed through the divergent portion and such calculations are carried out by starting from a given output of the tuyere. Under these conditions a shock wave will be producedin the divergent passage portion only when the flow rate of the blast is held within narrow limits, which in turn limits in certain cases the possibility of regulating the flow rate of the combustion supporting material, for example, the flow rate of the blast for a blast furnace.

While in certain applications such limitation of the regulation of the flow rate of the combustion sustaining material is acceptable, it is evident that better results will be obtained with a tuyere which permits a wide variation of the flow rate of the combustion sustaining material which is introduced into the tuyere.

SUMMARY OF THE INVENTION it is an object of the present invention to provide a method and an arrangement for operating a tuyere in such a manner to permit a relatively wide variation of the quantity per time unit of the combustion sustaining material introduced into the tuyere, while in each case assuring the formation of a shock wave in the divergent passage portion of the tuyere necessary for the proper atomization and mixing of the combustible material with the combustion sustaining material.

It is also an object of the present invention to provide for such an arrangement which is composed of relatively few and simple elements so that the arrangement can be produced at small cost and will stand up properly under extended use.

With these and other objects in view, the invention relates to a method to maintain, in a supersonic tuyere for the injection of combustible material, the pressure upstream of the divergent passage portion of the tuyere at least equal to a minimum pressure which assures formation of a shock wave in the divergent passage portion, despite relatively large variations of the flow rate of the combustion sustaining material as practically encountered during use of such tuyeres.

According to this method the pressure upstream of the convergent portion is compared with a reference pressure and the free area of the sonic neck of the tuyere is modified, preferably by axially displacing a central body arranged substantially coaxially in the convergent passage portion with reference to the neck in order to maintain the pressure at the upstream end of the tuyere in all cases at least equal to a minimum pressure which guarantees formation of a shock wave in the divergent passage portion, when the flow rate of the combustion sustaining material is varied within predetermined limits.

In a preferred method according to the invention the pressure upstream of the convergent portion of the tuyere is compared with a reference pressure, representing a pressure upstream of the tuyere of a magnitude which guarantees the formation of a shock wave in the divergent passage portion, and the central body is displaced with reference to the neck in the tuyere in such a manner to maintain the upstream pressure substantially equal to said reference pressure whenever the flow rate of the blast through the tuyere is changed.

The reference pressure may be an absolute, regulated pressure or a pressure measured at a downstream end of the tuyere to which a pressure differential A P is added, the value of which guarantees the formation of a shock wave in the divergent passage portion of the tuyere when the pressure at the downstream end of the tuyere is changed within limits as encountered during operation of the tuyere.

It is also an object of the present invention to provide an arrangement for carrying out the above method. The arrangement comprises a tuyere having a convergent passage portion and a divergent passage portion separated by a neck, means for feeding a combustion sustaining material, at an amount which may vary between predetermined limits, upstream of said convergent portion into the tuyere, means for feeding a combustible material in the region of the neck into the tuyere, a solid body arranged in the convergent portion and axially movable with respect thereto, means connected to the body for adjusting the position thereof relative to the neck, means to detect the pressure in the tuyere upstream of the convergent portion, means to furnish a reference pressure, means to compare said upstream pressure with said reference pressure and to produce a signal corresponding to the difference between these pressures, and means to transmit the thus obtained signal to the means to adjust the axial position of the body in order to displace the latter as a function of the magnitude of the signal in order to maintain the pressure in the tuyere upstream of the convergent portion, during variations within predetermined limits of the amount of combustion sustaining material fed into the tuyere, at such a pressure so as to produce a shock wave in the divergent portion to thereby atomize the combustible material fed in the region of the neck into the tuyere.

According to one embodiment of the present invention, the means for comparing the upstream pressure with a reference pressure comprise an enclosure having two compartments separated by a flexible membrane in which one face of the membrane is subjected to the aforementioned upstream pressure and the other face to the reference pressure. The flexible membrane is then deflected under the influence of the difference of the two pressures and such deflection constitutes a signal which is transmitted to the central body by connecting the deflected portion of the membrane to the central body. Such connecting means may comprise a simple mechanical connection or a more complex connection, for instance, electromechanical or fluid operated means operatively connected to the deflected portion of the membrane and to the central body to move the latter in axial direction corresponding to the deflection of the membrane portion.

According to a modification of the arrangement the reference pressure comprises the pressure at the downstream end of the tuyere to which a pressure differential A P is added which has a magnitude to assure formation of a shock wave at the divergent passage portion of the tuyere. In this modification, one of the two compartments of the enclosure may contain means to produce in the membrane a permanent deformation corresponding to the aforementioned pressure differential.

The present invention preferably also comprises means for cooling some elements of the arrangement, such as the aforementioned central body, which are exposed to heat radiation produced by the combustion of the material passing through the tuyere at the downstream end thereof. Such cooling means may be constituted by means for circulating a cooling fluid through such elements which are subjected to heating or by a solid member of high heat conductive characteristics which is cooled at one end and which contacts at the other end those elements in which rise of the temperature beyond a certain temperature should be prevented.

The invention, as understood', is concerned with finding a solution to the problem to properly regulate the output of a tuyere, to calculate a tuyere starting with a predetermined inlet pressure to obtain a perfect atomization of the combustible material fed into the tuyere, to vary the free cross section of the neck of the tuyere in accordance with variations of the flow rate of the blast in order to maintain the pressure upstream of the convergent passage portion at a pressure which assures production of a shock wave in the divergent passage portion.

As known, the mass output of a tuyere is given by the following formula:

m=KPil vTi-Ac wherein m is the mass output of the tuyere;

Pi the pressure upstream of the convergent passage portion; Ti the temperature of the gas or blast introduced into the tuyere; and Ac the free cross section of the neck of the tuyere. There are, therefore, two possibilities to change the mass output, that is either to vary Pi or to vary the free cross section of the neck. Since the magnitude of Pi is the sum of the atmospheric pressure plus the relative pressure, an upstream pressure is quickly reached which is incompatible with most industrial installations if a wide range of the mass output should be desired.

The other possibility which has been used in the present invention, consists in varying the free area of the sonic neck in order to obtain a change in the mass output. This possibility easily permits variations of the mass output within a ratio of l to 4 which satisfies any practical demand.

This variation of the cross section of the sonic neck is obtained by displacing a central body in the convergent passage portion of the tuyere while maintaining the position of the neck stationarily.

The adjustment of the position of the central body with regard to the sonic neck of the tuyere, in order to obtain a shock wave of substantially constant intensity during changes of the output, may be carried out in two different ways depending on the condition of the pressure existing atthe downstream end of the tuyere. In the first case, in which the pressure of the downstream end of the tuyere remains substantially constant, it is possible to maintain the upstream pressure by adjusting the position of the central body in accordance with the difference between the upstream pressure and a'constant pre-established reference pressure.

In the second case, in which the pressure at the downstream end of the tuyere varies with the output, the difference between the upstream and the downstream pressure may be maintained constant by displacing the central body in axial direction, which will result in an increase of the intensity of the shock wave and, therefore, in a perfect atomization of the combustion material.

In both cases, the geometrical characteristics of the tuyere, which are calculated in a manner well known in the art, are defined by starting from an upstream pressure compatible with a perfect atomization of the combustible material for a maximum output. It is to be understood, that in both cases, the form of the central body is calculated to accomplish the conditions set forth above under the assumption that the central body during its adjustment is maintained coaxial with the sonic neck. Such calculation is likewise well known in the art.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic axial cross section through a supersonic tuyere according to the present invention, used for injection of a combustible material into a blast furnace;

FIG. 2 is an axialcross section of a second embodiment of such a tuyere according to the present invention;

FIG. 3 is a schematic axial cross section of a further modification;

FIG. 4 is an axial cross section through the central body and illustrating means for cooling the same; and

FIG. 5 illustrates in axial cross section a modified arrangement for cooling the central body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and more specifically to FIG. 1 of the same, it will be seen that the arrangement according to the present invention comprises a supersonic tuyere 2 having a convergent passage portion 3, a sonic neck 4 and a divergent passage portion 5 downstream of the sonic neck. A curved conduit 1 is connected to the upstream end of the convergent portion 3 for feeding the blast, that is a combustion sustaining material into the supersonic tuyere. A solid body 6 of a profile calculated in accordance with the coordinates of the sonic neck is coaxially arranged in the convergent portion 3 movable in axial direction. As shown in FIG. 1, this body 6 may have a substantially conical configuration of substantially the same apex angle as the convergent portion 3. The body 6 is formed from refractory material, such as refractory steel and mounted at the end of a rod 7 displaceable in axial direction of the tuyere. The rod 7 is guided for movement in axial direction of the tuyere by guide means 8, schematically illustrated in FIG. 1, located in the portion of the conduit 1 which is coaxial with the tuyere. The central body 6 and the rod 7 are provided with means for coolingthe same in order to maintain their temperature at a level compatible with the nature of the material from which the body and the rod are formed. The means for cooling the body 6 and the rod 7 connected thereto will be described in detail later on. The rear or left-end, as viewed in FIG. 1, of the rod 7 passes with clearance through a tube 9, fluid tightly connected to the conduit 1, into an enclosure 10 divided by a flexible membrane 11 into two compartments, and the rear end of the rod 7 is fixedly connected, in any suitable manner, to the central portion of the membrane 11. The static pressure in the conduit 1 upstream of the convergent portion 3 of the tuyere is transmitted through the tube 9 to one face of the membrane II. A fixed reference pressure, delivered from a source of such a reference pressure through the conduit 12 to the other compartment of the enclosure 10, is applied to the other face of the membrane 11. The rod 7 connected to the membrane 11 transmits the deflection of the latter to the body 6.

The manner in which the combustible material, preferably a liquid fuel, is fed in the tuyere in the region of the sonic neck is not illustrated in FIG. 1 and the combustible material may be introduced into the region of the sonic neck into the tuyere passage in a manner known in the art, for instance through the wall of the tuyere, or by means of the central body 6 and the rod 7 connected thereto in the manner as will be described later on in detail or by a combination of the two aforementioned ways.

For a tuyere of a specific configuration, adapted for a maximum output andconstructed to function with a sonic shock wave, the pressure which has to be maintained at the upstream end of the tuyere is known.

Starting from this given data, it is possible to calculate the magnitude of the reference pressure which corresponds to an absolute pressure necessary in order to assure the formation of a shock wave. In order to adjust the cross section of the sonic neck to the output of the tuyere, the magnitude of the static pressure upstream of the convergent portion 3 of the tuyere is compared with the magnitude of the reference pressure, and when the difference between the two pressures is established, the area of the free cross section of the sonic neck is changed either by advancing the body 6 in axial direction towards the right, as viewed in FIG. 1, when the static pressure decreases, or by retracting the central body 6 towards the left, to increase the free cross section of the sonic neck, when the static pressure increases in such a manner so as to obtain an equalization between the upstream pressure and the reference pres sure.

In the example illustrated in FIG. 1, this comparison between the magnitude of the two pressures is obtained by directing the reference pressure and the upstream pressure, respectively to opposite sides of the deformable membrane ll. The deflection of the membrane 11 constitutes a signal which is transmitted by means of the rod 7 to the central body 6 to adjust the axial position of the latter, and to thereby adjust also the free cross section of the sonic neck 4. It will be understood from the above, that the amplitude of the deformation of the membrane 11 is determined in such a manner to provoke for each variation in the output a corresponding axial position of the body 6 relative to the sonic neck 4 to assure a proper function of the tuyere, that is, creation of a shock wave at the divergent portion 5 thereof.

FIG. 2 illustrates a second embodiment according to the present invention which is used when the pressure at the downstream end of the tuyere depends on the flow rate or the output of the blast. The elements of the arrangement shown in FIG. 2, which correspond to the elements shown in the arrangement of FIG. 1, are designated with the same reference numerals. The embodiment illustrated in FIG. 2 further includes an opening 13 in the divergent portion 5 of the tuyere connected by a conduit 14 to one of the chambers of the enclosure 10 so as to transmit the pressure at the downstream end of the divergent portion 5 to one face of the membrane 11 which is opposite to the face which receives through the tube 9 the pressure in the tube 1 upstream of the divergent passage portion 3. Regulating means, illustrated in FIG. 2 as a compression spring 15, permits to apply to the rear face of the membrane a supplementary pressure A P. The pressure A P may be adjusted exactly by means of an adjustment screw 16 threaded through a corresponding opening in the wall of the enclosure 10 and engaging the rear end of the compression spring 15. In this construction, regardless of the variations of the downstream pressure in the tuyere, there will always be an additional pressure A P of a magnitude which will guarantee that a shock wave will be formed at the divergent portion 5.

FIG. 3 schematically illustrates a further embodiment according to the present invention in which elements identical with those in the previously described embodiments are again designated with the same reference numeral. The embodiments illustrated in FIG. 3 differs from that as shown in FIG. 1 in that in the embodiment of FIG. 3 the rod 7 which projects rearwardly from the body 6 is not directly connected to the membrane 11, but connected thereto by means of fluid operated mechanism. As shown in FIG. 3, the pressure upstream of the convergent portion 3 of the tuyere 2 is transmitted through a conduit 9' to one compartment of the enclosure 10, whereas a fixed reference pressure .the two compartments. A rod 17 fixedly connected to a central portion of the membrane 11 projects fluid tightly guided through the wall of the enclosure and is connected at its outer end to the valverod 18 of a slide valve 19. The valve rod 18 carries in the interior of the cylinder of the slide valve two piston members 20 and 21 axially spaced from each other which, in the neutral position of the membrane 11, that is when the membrane is not deflected and the pressures in the two compartments are equal, close the inlet ends of a pair of conduits and 26, which are at their other ends are connected to a cylinder 23 in which a piston 24 is axially movable guided. Pressure fluid, preferably oil under pressure, is fed into the cylinder 19 of the valve by means of a conduit 22, opening in the cylinder between the two pistons 20 and 21. The conduits 25 and 26 are crossed, as shown in FIG. 3, so that the piston 25 will move, as will be clear from the following description, in the same direction as the pistons 20 and 21 are moved under the influence of any pressure difference in the two compartments of the enclosure 10. The piston rod 27 of the piston 24 is connected in any suitable manner to the rod 7 which in this embodiment is fluid tightly guided through an opening in the conduit 1 The above-described arrangement will operate as follows:

If the pressure transmitted to the right face of the membrane, as viewed in FIG. 3, is greater than the reference pressure transmitted to the other-face through the conduit 12, the central portion of the membrane 11 will be deflected toward the left, as viewed in FIG. 3, to thereby move the two valve pistons 20 and 21 also toward the left. Such movement of the valve pistons towards the left will open the inlet openings of the conduits 25 and 26 and pressure fluid, transmitted to the space between the two valve pistons through the conduit 22, will pass through the conduit 26 into the space of the cylinder 23 to the right of the piston 24 therein, to move the piston 24 towards the left, as viewed in FIG. 3, so as to retract the body 6 likewise toward the left, while pressure fluid in the space to the left of the piston 24 may pass through the conduit 25 into the valve cylinder 19 and flow out from the same through the discharge conduit 28. On the other hand, if the upstream pressure transmitted to the one compartmentof the enclosure 10 through the conduit 9 is smaller than the reference pressure, the membrane 11 will be deflected toward the right, as viewed in FIG. 3, so that, as will be evident from the preceeding description, the central body 6 will be moved correspondingly towards the right to restrict the open cross section of the sonic neck.

The enclosure 10 and the membrane extending transversely thereto which is subjected at opposite faces thereof to the upstream pressure and the reference pressure constitutes therefore a means to compare the upstream pressure of the tuyere with the reference pressure and to produce a signal, i.e., the deflection of the membrane, representative of the detected difference between such pressures.

In the embodiment shown in FIG. 3 the abovedescribed elements between the membrane 11 and the rear end of the rod 7 constitute means to transmit the signal to the means, i.e., the rod 7, to adjust the axial position of the body 6. In'the embodiments shown in FIGS. 1 and 2, the means to transmit the signal, that is the deflection of the membrane 11 to the means to adjust the axial position of the body 6, that is to the rod 7, is constituted by the mechanical connection between the membrane and the rear end of the rod 7.

FIGS. 45 and 5 schematically illustrate means for cooling the body 6 and the rod 7 connected thereto. in the embodiment shown in FIG. 4, the rod 7 is tubular and it extends with its front or right end, as viewed in FIG. 4, into the hollow central body 6, while its enlarged rear end abuts with its rear wall against one face of the membrane 11 and is tightly held against this face by a nut 30 screwed onto an extension of the tubular rod 7' which projects through an opening in the membrane 11. A tube 31 coaxially arranged within the tubular rod 7', radially spaced therefrom, extends with a closed substantially conical end into a conical cavity formed in the body 6. A second tube 33 is coaxially arranged within the tube 31 also radially spaced therefrom and this inner tube 33 ends with its open end short of the closed end of the tube 31, whereas the rear end of the tube 33 extends through the closed rear end of the tube 31. The combustible material, which is preferably a liquid fuel, is fed into the enlarged end 7a of the tubular rod 7' through a flexible conduit 29 which passes, in a manner not shown in FIG. 4, fluid tightly through one wall of the enclosure 10 described above and is connected to a source of a fuel supply not illustrated in the drawings. The liquid fuel thus entering in the space between the inner surface of the tubular rod 7 and the outer surface of the tube 31 passes into the cavity of the body 6 and leaves the latter through a plurality of outlet bores 6'. A cooling fluid is fed through a flexible conduit 32 into the rear end of the tube 31 to flow in the space between the inner surface of the tube 31 and the outer surface of the tube 33 toward the closed front end of the tube 31 and to pass out from the latter through the inner tube 33. The flexible conduit 32 passes likewise through a wall of the compartment 10 and is connected to a source of cooling fluid (not shown), whereas the discharged cooling fluid passes into an appropriate container, not shown in the drawing, or the discharged cooling fluid may be recirculated to enter again through the conduit 32 intothe interior of the tube 31.

In the embodiment shown in FIG. 5, the fuel is passed to the outlet bores 6 in the hollow body 6 through a central tube 36 connected at its right end by welding or in any suitable manner to the body 6, whereas the cooling fluid is fed into the enlarged portion 7a" of the tubular rod 7 by means of a flexible conduit 34 and the front end of the tubular rod 7" is again connected by welding or in any similar suitable manner to the body 6. A tube 35, arranged coaxial with the tube 36 and the tubular rod 7" and intermediate these two tubes, permits return flow of the cooling fluid introduced into the tubular rod 7" through a flexible conduit 34 and the cooling fluid leaves the interior of the tube 35 through a flexible conduit 37. At least the inner tube 36 of the arrangement shown in FIG. 5 is made from a material having a high heat conductive characteristic so that the body 6 is not only cooled by the cooling fluid passing through the rear part thereof, but also by heat convection through the cooled inner tube 36.

it is also possible to modify the arrangement shown in H6. by not circulating a cooling fluid about the inner tube 36 but by forming the rod 7 just with an axial bore therethrough and by cooling the rear end of the rod distant from the head 6, for instance, by evaporation of a liquid, so that heat from the body 6 is withdrawn only by heat convection through the rod which, as mentioned before, has to be formed from a material having a high heat conductive characteristic. If a fuel is not to be injected into the interior of the tuyere through fuel outlet openings in the body 6 as shown in M68. 4 and 5, then evidently the central bore through the rod 7 may be omitted and the rod used only for transmitting the deflection of the membrane 11 to the body 6 and to cool the latter by heat convection. The described arrangements in which no cooling fluid is circulated through the tubular rod has the advantage over the arrangements shown in FIGS. 4 and 5 that no cooling fluid can enter the tuyere in the event of some leakage.

it will be understood that each of the elements described above, or two or more together may also find useful application in other types of supersonic tuyeres differing from the types described above.

While the invention is illustrated and described as embodied in a tuyere constructed and controlled to produce a shock wave in the divergent portion of the tuyere, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. For instance, instead of the fluid operated mechanism which connect, as shown in FIG. 3, the central portion of the membrane with a rod 7 it is also possible to use electromechanic or electronic arrangements for moving the rod 7 in correspondence with the deflection of a central portion of the membrane.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

able with respect thereto; motor means connected to said body for adjusting the position thereof relative to said neck; means to detect the pressure in said tuyere upstream of said convergent portion; means to furnish a reference pressure; means to compare said upstream pressure with said reference pressure and to produce a signal corresponding to the difference between said pressures; and means to transmit said signal to said motor means for adjusting the axial position of said body in order to displace the latter as a function of the magnitude of said signal in order to maintain the pressure in said tuyere upstream of the convergent portion during variations, within said predetermined limits, of the amount of combustion sustaining material fed into said tuyere, at such a pressure to produce a shock wave in said divergent portion so as to atomize the combustible material fed into the tuyere in the region of said neck.

2. A combination as defined in claim 1, wherein said means to compare said upstream pressure with said reference pressure comprises an enclosure, a membrane extending transversely through said enclosure and dividing the latter into two separate compartments, and means for applying said upstream pressure to one face of said membrane and for applying said reference pressure to the other face of said membrane so as to deflect a portion of the latter in correspondence to the difference between said pressures.

3. A combination as defined in claim 1, wherein said body is of substantially conical configuration tapering towards said divergent portion and having an outer maximum diameter smaller than the inner diameter of said neck. v

4. A combination as defined in claim 1, wherein said means to compare said upstream pressure with said reference pressure comprises an enclosure, a membrane extending transversely through said enclosure and dividing the same into two separate compartments, and means for applying said upstream pressure to said one face of said membrane and for applying said reference pressure to the other face of said membrane so as to deflect a portion of said membrane in correspondence with the difference of said pressures, and wherein said motor means to adjust the axial position of said body as a function of the deflection of said portion of said membrane comprises a cylinder and a piston reciprocatable in said cylinder and connected to said body for moving the same in axial direction, and means connected to said portion of said membrane for feeding pressure fluid into said cylinder to one or the other side of the piston therein to move the latter and the body connected thereto in axial direction and in correspondence with the deflection of said membrane portion.

5. A combination as defined in claim 1, and including means for cooling said body. 

1. In a supersonic tuyere having a convergent passage portion and a divergent passage portion separated by a neck, a combination comprising means for feeding a combustion sustaining material at an amount, which may vary between predetermined limits, upstream of said convergent portion into said tuyere; means for feeding a combustible material in the region of said neck into the tuyere; a solid body coaxially arranged in the said convergent passage portion and axially movable with respect thereto; motor means connected to said body for adjusting the position thereof relative to said neck; means to detect the pressure in said tuyere upstream of said convergent portion; means to furniSh a reference pressure; means to compare said upstream pressure with said reference pressure and to produce a signal corresponding to the difference between said pressures; and means to transmit said signal to said motor means for adjusting the axial position of said body in order to displace the latter as a function of the magnitude of said signal in order to maintain the pressure in said tuyere upstream of the convergent portion during variations, within said predetermined limits, of the amount of combustion sustaining material fed into said tuyere, at such a pressure to produce a shock wave in said divergent portion so as to atomize the combustible material fed into the tuyere in the region of said neck.
 2. A combination as defined in claim 1, wherein said means to compare said upstream pressure with said reference pressure comprises an enclosure, a membrane extending transversely through said enclosure and dividing the latter into two separate compartments, and means for applying said upstream pressure to one face of said membrane and for applying said reference pressure to the other face of said membrane so as to deflect a portion of the latter in correspondence to the difference between said pressures.
 3. A combination as defined in claim 1, wherein said body is of substantially conical configuration tapering towards said divergent portion and having an outer maximum diameter smaller than the inner diameter of said neck.
 4. A combination as defined in claim 1, wherein said means to compare said upstream pressure with said reference pressure comprises an enclosure, a membrane extending transversely through said enclosure and dividing the same into two separate compartments, and means for applying said upstream pressure to said one face of said membrane and for applying said reference pressure to the other face of said membrane so as to deflect a portion of said membrane in correspondence with the difference of said pressures, and wherein said motor means to adjust the axial position of said body as a function of the deflection of said portion of said membrane comprises a cylinder and a piston reciprocatable in said cylinder and connected to said body for moving the same in axial direction, and means connected to said portion of said membrane for feeding pressure fluid into said cylinder to one or the other side of the piston therein to move the latter and the body connected thereto in axial direction and in correspondence with the deflection of said membrane portion.
 5. A combination as defined in claim 1, and including means for cooling said body. 